i'm sure you'll get a slew of "white subway tile" suggestions.

I like this one from Tilebar. Nabi Rocky Edge in gun metal. go over there and grab some samples. you get 5 for $5.

The Nabi line comes in this Arctic blue too. grab a sample of it also

I also like the soft blue color you have on the walls. Could do something like the blue?

These are from Heath Ceramics.

diff blue tones in a stacked horizontal or vertical layout

or you could do any other color.

these are both 2x10 tiles in more of a handmade look. this one has the mushroom tones:

grayish/taupe tile from Winchester. Dunwich, in a crackle glaze

since everything is solid, you could also opt for a diff shape tile

or take a subway and do a herringbone pattern.

there are thousands of options. could you narrow down the choices a bit??

https://www.tilebar.com/nabi-gunmetal-3x6-ceramic-tile.html

here's the link.

and the Nabi line comes in diff colors and shapes. I also like the Harlequin

https://www.tilebar.com/collection/tile-mosaic-collections/nabi.html

Some color is in order here - no boring blah white subway! I think you can do pretty much any color you want with your cabinet/countertop combo but if you want to keep things soft and in-line with a "mushroom" color paint, a backsplash in soft light blues or greens would look lovely.

Any color suggestions?